Surgical prosthetic mesh has been used to treat or reinforce tissues or organs which have been damaged, prolapsed, weakened, or otherwise herniated, such as in the conditions rectocele, cystocele, enterocele, vaginal prolapse, and protocele, for example. A prolapse refers to the slipping down of an organ or organ part from its normal position. For example, a prolapse of the rectum refers to the protrusion of the inner surface of the rectum through the anus. Rectocele is the prolapse of the rectum into the perineum. A prolapse of the uterus refers to the falling of the uterus into the vagina due to stretching and laxity of its supporting structures. Vaginal vault prolapse refers to the prolapse of the cephalad extreme of the vaginal canal toward, through, and beyond the introitus. Cystocele (i.e., vesicocele) is a hernia formed by the downward and backward displacement of the urinary bladder toward the vaginal orifice, due most commonly to weakening of the musculature during childbirth. However, any abnormal descent of the anterior vaginal wall and bladder base at rest or with strain is considered cystocele. Enterocele is a hernia of the intestine, though the term is also used to refer specifically to herniation of the pelvic peritoneum through the rectouterine pouch (i.e., posterior vaginal, rectovaginal, cul-de-sac, or Douglas' pouch hernia).
Surgical mesh may also be used to suspend tissues or retract body organs temporarily, e.g., during surgery. For example, U.S. Pat. No. 4,973,300 describes the use of a cardiac sling for supporting the heart during surgery; and U.S. Pat. No. 5,362,294 describes the retraction of body organs such as the uterus or bowel during laparoscopic surgery; U.S. Pat. No. 6,102,921 describes the use of a medical anastomosis sling for the use in repair or regeneration of nerves.
Synthetic mesh materials utilized as slings for the treatment or reinforcement of patient tissues for these and many other conditions can cause patient complications such as erosion, due at least in part to the sharp tangs on the edges of the mesh, which are formed during the manufacturing process or afterward (for example, when a physician cuts or shears or otherwise shapes the material). These tangs can cause an irritative effect which can lead to an erosion when they contact surrounding tissue. Thus, a need exists for a sling which minimizes irritation and erosion of the tissue surrounding the tissue which it supports.
Stress urinary incontinence (SUI), which primarily affects women, is a condition which is successfully treated using surgical slings. Stress urinary incontinence is generally caused by two conditions that may occur independently or in combination, namely, intrinsic sphincter deficiency (ISD) and hypermobility. In ISD, the urinary sphincter valve, located within the urethra, fails to close properly (coapt), causing urine to leak out of the urethra during stressful actions. Hypermobility is a condition in which the pelvic floor is distended, weakened or damaged, causing the bladder neck and proximal urethra to rotate and descend in response to increases in intra-abdominal pressure (e.g., due to sneezing, coughing, straining, etc.), resulting in insufficient response time to promote urethral closure and, consequently, in urine leakage and/or flow.
Biological factors that can affect hypernobility include: poor endopelvic fascia muscle tone (from age or limited activity), endopelvic fascia muscle stretch/tear from trauma (e.g. childbirth), endopelvic fascia/arcus tendenious (muscle/ligament) separation (lateral defect), hormone deficiency (estrogen), concombinant defects (cystocele, enterocele, ureteral prolapse), and vaginal prolapse. Traditional treatment methods include bladder neck stabilization slings in which a sling is placed under the urethra or bladder neck to provide a platform preventing over distention. An emerging alternative treatment is the placement of a mid-urethral sling. Such a sling placement takes advantage of the hypermobility condition by providing a fulcrum about which the urethra and bladder neck will rotate and provide a “urethral kink” to assist normal urethral closure.
Slings are traditionally placed under the bladder neck to provide a urethral platform limiting endopelvic fascia drop while providing compression to the urethral sphincter to improve coaptation. The mid-urethral placement location provides mechanical stability to a less moveable anatomical structure. Bladder neck slings have traditionally been affixed in the desired location using a bone anchoring method. Mid-urethral slings, being placed in a low mobility area, have demonstrated the effectiveness of an anchorless approach. Recognizing that minimal tension, if any, is necessary, a physician need only place the sling under the mid-urethra secured through the endopelvic fascia to permanently secure the sling in position. The sling permits immediate tissue security through the mesh openings and mesh tangs to initially maintain sling stabilization. As healing occurs, the endopelvic fascia and rectus fascia tissue re-establish vascularity and regrow into and around the knit pattern of the mesh. The sling in this procedure provides a fulcrum about which the pelvic floor will drop (taking advantage of the hypermobility condition of the patient) and a urethral “kink” or higher resistance to obstruct urine flow during high stress conditions.
Thus, while tangs can contribute beneficially to SUI treatment, they can also cause patient complications such as erosion of the vagina or urethra.